@Gershuun: You cannot cage a pet that is in your battle area. Most likely that is your problem. Open your Pet Journal and make sure none of the 3 pets on your battlefield are not him. Then you should be able to right click on Laughing Stonekin and choose "put in cage".

Other than that, nothing special to me about this Panderian elemental vs mechanical pet except I like the idea of mudslide in slot 3.